High temperature lubricating grease containing a p, p&#39;-diaminodiphenylether



United States Patent HIGH TEMPERATURE LUBRICATING GREASE EOIlTIII'IJIAINING A p,p DIAMINODIPHENYL- T No Drawing. Filed Apr. 2, 1958, Ser. No. 725,808

7 Claims. (Cl. 2 52-40.7)

' This invention relates to high temperature lubricating grease of improved stability for use under the more severe conditions of modern technology. This application is a continuation-in-part of copending application Serial No. 545,513, filed November 7, 1955 and now abandoned.

During recent years developments in aircrafts, turbines, automobiles, trucks, farm equipment, railroad equipment, industrial machinery, etc. have resulted in equipment operating at higher temperatures, higher speeds and greater loads. These developments have presented new problems in the satisfactory lubrication of such equipment and require lubricating greases which will be efiective under these more severe conditions. viously available were found wanting because of instability at the higher temperatures. A

The new problems presented by these developments are illustrated, for example, in the turbo jet engines, where satisfactory lubrication is required at temperatures ranging from as low as -65 F. and as high as 275 F. during use. Temperatures up to 500 F. are encountered at intervals of from one to two hours during shutdown. New developments in winter grade crank case oils, aviation instruments, automatic weapons, etc. are additional examples of recent developments which have presented new problems in lubrication. As hereinbefore set forth, there is a great need for lubricating greases which are stable during use under these severe conditions. In addition, these greases should be useable for longer times and, therefore, improved stabilityis essential.

In accordance with the present invention, improved stability is imparted to lubricating grease by incorporating therein an inhibitor of specific configuration. As

will be illustrated in the appended examples," the inhibitors of the present invention appear" to be peculiarly advantageous in lubricating greases and particularly during use at high temperatures, high speeds and with greater loads. In contrast thereto, it will be noted that similar but diiferent additives do not impart this high stability to the lubricating grease.

Greases -pre' uze These greases are solid or semi-solid gels and in general are prepared by the addition to mineral oils of hydrocarbon-soluble metal soaps or salts of higher fatty acids as, for example, lithium stearate, calcium stearate, aluminum naphthenate, etc. In another method, the metal soap or salt is added to synthetic oils including, for example, di-(Z-ethylhexyl) sebacate or azelate, di-tetradecyl sebacate, tricresyl phosphate, polyalkylene oxides, silicones, alkyl or alkylaryl polysiloxanes or blends of these with petroleum oil. The grease may contain thickening agents such as silica, Bentonite, carbon black, polyacrylates, talc, polyamides, alkylureas, phthalocyanines, etc. Another type of grease is prepared from oxidized petroleum wax to which thesaponifiable base ing concentration of a p,p-diaminodiphenyl ether inhibitor.

In a specific embodiment the present invention relates to a method of stabilizing a high temperature lithium base lubricatinggrease which comprises incorporating therein from about 0.001% to about 5% by weight of p,p'-diaminodiphenyl ether.

In another specific embodiment the present invention relates to a method of stabilizing a high-temperature calcium base lubricating grease which comprises incorgporating therein from about 0.001% to about,5% by The high temperature lubricating greases of the present invention generally include lithium base grease, sodium base grease, potassium base grease, barium base grease, strontium ,base grease, aluminum base grease,

beryllium base grease, cadmium base grease, magnesium base grease, lead soap grease, complex soapgrease, etc.,

or mixtures known as mixed base greases including barium-calcium, barium-lithium, sodium-calcium, sodium-barium, aluminum-lithium," lithium-strontium,- etc.

weight of p,p'-diisopropylaminodiphenyl ether.

tered at these conditions, the inhibitorof the presentinvention also serves to deactivateor passivate the effect of metals contained in or contacted by .the grease. In many cases such metals. tend to catalyze oxidation and other undesirable deterioration of the grease. However, this undesirable effect is offset by, the novel inhibitors of :the present invention.

In one embodiment, the inhibitor of the present invention comprises p,p'-diaminodiphenyl ether. In another embodiment, the inhibitor comprisesa p,p'-dialkylaminodiphenyl ether.

nitrogen atom at an intermediate carbon atom of 'the alkylgroup. Illustrative compounds in this-class include 1 p,p'-diisopropylaminodiphenyl ether, p,p"-di sec-.butyl-.

In the latter embodiment, it gen-, erally is preferred that the alkyl groups areofsecondary I configuration; .that is, th'ealkyl group is attached to the 3 aminodiphenyl ether, p,p di sec amylaminodiphenyl ether, p,p' di sec hexylaminodiphenyl ether, p,p' di sec heptylaminodiphenyl ether, p,p' di sec octylaminodiphenyl ether, p,p'-di-sec-nonylaminodiphenyl ether, p,p-di-sec-decylaminodiphenyl ether, p,p-di-secundecylaminodiphenyl ether, p,p'-di-sec-dodecylaminodis phenyl ether, p,p'-di-sec-tridecylaminodiphenyl ether, p, p'-di-sec-tetradecylaminodiphenyl ether, p,p-di-sec-pentadecylaminodiphenyl ether, p,p-di-sec-hexadecylaminodiphenyl ether, p,p-di-sec-heptadecylaminodiphenyl ether, p,p'-di-se c-octadecylaminodiphenyl ether, p,p-di-sec-nonadecylaminodiphenyl ether, p,p'-di-sec-eicosylaminodiphenyl ether, etc.

While compounds containing secondary alkyl groups are preferred, it is understood that suitable compounds containing n-alkyl substituents may be employed, but not necessarily with equivalent results. Illustrative compounds in this class include p,p-dimethylaminodiphenyl ether, p,p'-diethylaminodiphenyl ether, p,p-di-n-propylaminodiphenyl ether, p,p'-di-n-butylaminodiphenyl ether, p,p-di-n-amylaminodiphenyl ether, p,p'-di-n-hexylaminodiphenyl ether, p,p-'-di-n-heptylaminodiphenyl ether, p,pdi-n-octylaminodiphenyl phenyl ether, p,p-di-n-decylaminodiphenyl ether, p,p-din-undecylaminodiphenyl ether, p,p-di-n-dodecylaminodiphenyl ether, etc. a

In' general it is preferred that the inhibitor comprises a symmetrical compound; that is, the alkyl groups are of the same configuration and chain length. However, in some cases the alkyl groups may be different in either the number of carbon atoms or in the configuration thereof, or both, and preferably are selected from the alkyl groups hereinbefore specifically set forth. In another embodiment the hydrocarbon radicals attached to the nitrogen atoms may comprise alkenyl groups as, for example, in compounds such as p,p-dipropenylaminodiphenyl ether, p,p'-dibutenylaminodiphenyl ether, p,pdipentenylaminodiphenyl ether,v p,p-dihexenylaminodiphenyl ether, p,p'-di-heptenylaminodiphenyl ether, p,pdioctenylaminodiphenyl ether, etc., which alkenyl groups preferably are of secondary configuration.

From the above description, it will be noted that a number of different inhibitor compounds may be used in accordance with the present invention. However, it is understood thatthe diiferent compounds are not necessarilyequivalent. The specific compound to be used will depend upon the availability and/or cost of preparation and also upon the effectiveness in the particular grease.

to bestabilized. .It is understood that a mixture of compounds may beemployed, the particular compounds preferably being selected from those hereinbefore specifically set forth. In some cases, a mixture of isomers is produced during the manufacture of the inhibitor and, when desired, the mixture is used as such, thereby avoiding the additional time and expense of separating the components of the mixture. 7 V

In general, the inhibitor is utilized in a concentration of from about 0.001% to about 5 by weight of the grease, although in some cases higher or lower concentrations may be employed. The exact concentration to be fused will depend upon the particular grease being treated In most cases a concentration of from about 0.01% toabout 3% by weight generally is employed.

It" is understood thatthe inhibitor may be used along 7 with other additives incorporated in grease, including a activator -as, for example, disalicylai diamino propane, 'ethylene diamine tetra-acetic acid or the tetrasodium salt thereof, etc., or to include' oth'er additives such as tricresyl phosphate,1trialkyl phenols, including 2,6-di-tertbutyl 4-rnethylphe nol, -2,4-di-methyl-6rtert-butyl-phenol,

alkylated diphenyl amines, phenyl naphthyl amines, jdiether, p,p'-di-n-nonylam1nodia in a lithium grease.

in}; 91% of a highly refined Pennsylvania oil having a aminodiphenyl ether.

alkyl phenylene diamines, phenothiazine, organic selenium compounds, etc., as well as corrosion inhibitors, extreme pressure additives, viscosity index irnprovers, etc. When desired, the inhibitor of the present invention may be prepared as a mixture with one or more of these other additives and incorporated in this manner in the grease or components thereof.

The inhibitor of the present invention may be incorporated in the grease in any suitable manner and at any suitable stage of preparation. Thus, it may be added to one or more components of the grease prior to compositing and processing thereof or it may be added to the mix at any time, preferably before final processing in order to obtain intimate mixing and dissolving of the inhibitor in the grease.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I Calcium base grease is prepared by the following general method. The calcium soap is prepared by mixing the fat, hydrated lime equivalent to about one-seventh of the'fat, mineralv oil suificient to make about onefourth of the total charge, and about 0.5% of Water. The ingredients are mixed and heated to about F. and thendry lime is added, agitation and heat continued until saponification is completed; Additional oil then is added and the mixture heated to 220230 F. Additional oil is added to bring the mixture to the desired consistency, and then is heated at -180 F. At this stage, 1% by weight of p,p-di-sec-butylaminodiphenyl ether, along with other additives, dyes, etc. is added, and the mixing is continued until formation of grease of the desired structure.

EXAMPLE II p,p-diaminodiphenyl ether was utilized as an inhibitor The grease was prepared 'by mix- Sayboit viscosity of 180 second at 100 F. with 8% of tithium stearate. The mixture was heated to about 450 F. while agitating the same. Subsequently, the grease was cooled to 3209-1 while agitating and, at this temperature, 1% of p,p-diaminodiphenyl ether was added. Agitation was continued and the mixture was allowed to cool to about 250 F., and the grease then further cooled slowly to room temperature.

The stability of the grease was tested according to a modified Norma Hoffman method, in which a sample of the grease is placed in a bomb in the presence of brass discs acting as an oxidation catalyst and oxygen is charged thereto. The bomb then is heated to 212 F., and the time required for a drop of 5 pounds pressure is taken as the induction period. In this run, a control sample of the grease (not containing this additive) had an induction period-of 4 hours. On the other hand, a sample of the grease containing 1% by weight of p,p-diaminodiphenyl ether had an induction period of 187 hours. Thus, it=will be noted that the inhibitor of the present invention was exceptionally effective in improving the The inhibitor used in this example is p,p'-diisopropyl- When incorporated. in a. concentration of 1% by weight to another sample of the grease described in Example II and tested in the same manner, the inhibitor of this. example served, to increase the induction period of the; grease-from 4 hours to 133 hours. Here again, it willbe noted. that the'inhibitor of the present invention servedtostabilize the grease toa considerable extent. j EXAMPLE 1v perature.

Table 1 Induction period Inhibitor (Hours to 5 pounds pressure drop) N one. 2 0.3% by weight of p,p-diarninodiphenyl ether 215 0.3% by weight of p,p-diisopropyldiaminodiphenyl ether 200 0.3% by weight of p,p'-totramethyldiammodiphenyl methane 9 From the data in the above example it will be noted that the diaminodiphenyl ethers were very efiective in improving the stability of the grease at the high tem- In contrast, the diaminodiphenyl methane was substantially of no value. This demonstrates the unique properties of the diaminodiphenyl ether to impart high stability to the lubricating grease in contrast to the absence of this property in the diaminodiphenyl methane, even though the latter may be said to be of similar chemical configuration to the diaminodiphenyl ether.

EXAMPLE V This example reports additional evaluations in a different lithium base grease than reported in Example IV.

The lithium base grease also contained 8% by weight of lithium stearate but was prepared with a different mineral oil. When evaluated under the same conditions as re- Here again, the peculiar properties of the diaminodiphenyl ether in high temperature grease is demonstrated. It will be noted that three-tenths the concentration of diaminodiphenyl ether yielded a grease having the stability of more than three times that obtained with the diaminodiphenyl methane. Even the use of one-tenth as much diaminodiphenyl ether still produced a grease of higher stability than that obtained by using 1% by weight of diaminodiphenyl methane.

EXAMPLE v1 eral oil, and the evaluations were made in the same manner as described in Example H.

Table III Induction period Inhibitor (Hours to 5 pounds pressure p) None 8 1% by Weight of p,p-diaminodiphenyl ether 93 1% by weight of p,p-di-sec-butylaminodiphenyl methane 22 1% by weight of p,p-dioctylaminodiphenyl methane. 27 1% by weight of p,p'-dibeuzylamiuotriphenyl methane 23 From the data in the above table, it will be noted that the diaminodiphenyl ether is many times more effective than the diaminodiphenyl methanes and the diaminotriphenyl methane shown in the above table.

The data in the above examples demonstrate the peculiar effectiveness of the diaminodiphenyl ethers to impart high stability to lubricating greases. This effectiveness is especially important to lubricating greases when used at high temperatures. These improved results are outstanding,-particularly when compared with the lack of effectiveness of the diphenyl methanes at these high temperatures. Furthermore, as seen from the data in Example VI, the superiority of the diphenyl ethers also is evidenced even when the grease is evaluated at the lower temperature.

We claim as our invention:

I 1. A lubricating grease composition consisting essentially of a major amount of a lubricating oil, a greasethickening amount of a metal soap of a higher fatty acid and a stabilizing concentration of a p,p'-diaminodiphenyl ether.

2. A lubricating grease composition consisting essen- V tially of a major amount of a lubricating oil, a grease- 'As demonstrated by Examples IV and V, the diamino- Q diphenyl ethers impart high stability to the greases evaluated at the higher temperature. This effect is peculiar to the diaminodiphenyl ethers and is not obtained with.

diaminodiphenyl methanes. While this improvement at high temperatures is extremely important for the reasons hereinbefore set forth, the following data show that the diaminodiphenyl ethers are considerably more effective than the diaminodiphenyl methanes even when evaluated at the lower temperature of 210 F. and in the presence thickening amount of a metal soap of a higher fatty acid and from about 0.001% to about 5% by Weight of p,pdiaminodiphenyl ether.

3; A lubricating grease composition consisting essentially of a major amount of a lubricating oil, a greasethickening amount of a metal soap of a higher fatty acid and from about 0.001% to about 5% by weight of a p,p'- dialkylaminodiphenyl ether.

4. A lubricating grease composition consisting essentially of a major amount of a lubricating oil, a greasethickening amount of a lithium soap of a higher fatty acid and from about 0.01% to about 3% by weight of p,p'-diisopropylaminodiphenyl ether.

5. A lubricating grease composition consisting essentially of a major amount of a lubricating oil, a greasethickening amount of a lithium soap of a higher fatty acid and from about 0.01% to about 3% by weight of p,p'-di-sec-butylarninodiphenyl ether.

6. Alubn'cating grease composition consisting essentially of a'major amount of a lubricating oil, a greasethickem'ng amount of a calcium soap of a-higher fatty acid and from. about 0.01% ,to about 3% by weight of p,p'-diisopropylaminodiphenyl ether.

7. A- lubricating grease composition consisting essentially of a major amount of a lubricating oil, a greasethickening amount of acal'cium' soap of a higher fatty acidand fromabout 0.01% to about 3% by weight of p,p'-di-sec-butylaminodiphenyl ether.

References Cited in the file of this patent 1 UNITED STATES PATENTS 2,910,437 i Symon Oct. 27, 1259 

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A LUBRICATING OIL, A GREASETHICKENING AMOUNT OF A METAL SOAP OF A HIGHER FATTY ACID AND A STABILIZING CONCENTRATION OF A P,P''-DIAMINODIPHENYL ETHER. 